Prescription drugs have become an indispensable tool to treat and manage chronic disease, and the utilization and cost of drugs have dramatically increased in the past decade. As drug costs have grown, access to drugs has decreased for both the insured and uninsured. For the uninsured, paying one hundred percent of the cost of drugs has made adhering to drug regimens difficult. Similarly, the insured have suffered reductions in benefits from insurers trying to control spiraling costs. Because drug therapy is the standard treatment for many chronic illnesses, the interruption or lack of drug therapy can have serious health consequences. Thus, the chronically ill may be particularly vulnerable to changes in utilization mediated by insurance. While some research has measured the effect of insurance status and benefits on the use and cost of drug regimens for the chronically ill, virtually no research has examined these same effects for persons with multiple chronic illnesses. This project aims to compare how insurance status, insurance benefits, and the price of disease-specific medications affect the drug treatment regimens for persons with two chronic conditions relative to persons with only one of the two conditions. To accomplish these aims, this study will utilize a large claims database of privately-insured individuals and the Medical Expenditure Panel Survey. Analysis will include multi-variate regression techniques to estimate: 1) how the use and duration of disease-specific medications are affected by insurance status and benefits design for persons with a single chronic condition and with multiple conditions; and 2) how price-sensitive these populations are to different disease-specific drug classes. [unreadable] [unreadable] [unreadable]